Post on 20-Aug-2020
transcript
Alkali-Silica Reactivity (ASR)Aggregate Testing: Is There a Better, Quicker, and More Reliable Method?
Current Aggregate Tests Originate from 1947
• Mielenz, Greene, and Benton American Concrete Institute (ACI), 1947
• Sprague Hun et al. (ACI), 1948• 1N Sodium Hydroxide 80 °C• Measured Mortar Bar Expansion
• ASTM C 289 — Test has poor reliability. • Petrography — Tool is useful but depends
on skill of petrographer.• ASTM C 227 — Test can result in leaching.• ASTM C 1260 — Test can be overly severe.• ASTM C 1293 — Testing period is lengthy
and can result in leaching; test is unsuitable for the evaluation of job mix design.
Aggregates
Mortar
Concrete
Current ASR Test Methods
ASTM – American Society for Testing Materials
ASTM C1778 – 16
Standard Guide for Reducing the Risk of Deleterious Alkali-Aggregate Reaction in Concrete
Reprinted, with permission, from Standard Guide for Reducing the Risk of Deleterious Alkali-Aggregate Reactionin Concrete, copyright ASTM International, 100 Barr Harbor Drive, West Conshohocken, PA 19428. A copy of the complete standard may be obtained from ASTM International, www.astm.org.
“Is my particular job mix design reactive?”
Yes/No
Add Supplementary Cementitious Materials (SCMs)
TFHRC Chemical ASR Test
Standard Methods • ASTM 1260 — Rapid but inaccurate.
• ASTM 1293 — More accurate but takes 1 to 2 years for results.
Source: FHWA
Source: FHWA
TFHRC Test – Pure Chemistry
• Mill report.• Mix design.• 5-gram
aggregate.• 21 days.
3.125 gRet. #50(297 µm)
1.875 gRet. #100(149 µm)
Source: FHWA
TFHRC Chemistry LaboratoryResearch Since 2009
• Researchers in TFHRC’s Chemistry Lab studied the chemistry of ASR gels. Findings include:– ASR gel has no unique composition.– Chemical composition of gels affect structure, which affects
expansion.– The Raman Spectroscopy study helped identify what chemical
parameters are important in a test.
Must Test The Job Mix• Meaningless to test aggregate alone.• Thirty job mixes tested per person per week.• Only 1 measurement is needed at the end of 21
days.
ASRTESTS
Aggressive Environment Possibility
to test job mix
Realistic concrete
pore solution
Testing period
Mirrorfield
performance
TestingEfficiencyAlkali
conc. Temp.
ASTM 1260 Yes Yes No No 14
days No Medium
ASTM1293 Yes No No No 1 year Mostly Low
TFHRC Chemical
TestNo No Yes Yes 21
days Yes High
Comparison of Accelerated ASR Tests
conc. - concentration
Results: Correlation with Physical ExpansionExpansion
No ExpansionFalse Positive
False Negative
Source: FHWA
Correlation with Physical Expansion ASTM C1260Expansion
No ExpansionFalse Positive
False Negative
MassDOT
TxDOT
Source: FHWA
Correlation with Physical Expansion ASTM 1293
Expansion
No ExpansionFalse Positive
False Negative
Source: FHWA
Correlation with Physical Expansion - TFHRC TestExpansion
No ExpansionFalse Positive
False Negative
Source: FHWA
Calibration of TFHRC ASR Test• Field cases, block farms, or structures:
– Aggregate samples 500 g.– Cement samples 50 g or mill certificate.– Mix design.– Expansion data (new and historical).
• The test can accurately detect highly and nonreactive coarse aggregates.
• Intermediate reactive aggregates are more challenging to detect.
• Comparison of lab test results with known field block expansion shows good correlation.
TFHRC Rapid Chemical ASR Test
Terry ArnoldSenior Research ChemistFederal Highway Administration (FHWA)Turner-Fairbank Highway Research Center (TFHRC)Office of Infrastructure Research and Development (R&D)6300 Georgetown PikeMcLean, Virginia 22101 Terry.Arnold@dot.gov202–493–3305
We are looking for field cases and block farm data to further populate the calibration charts.
Contact Us!
The Way Forward